Fiberglass and other solid filter media used in air filters, e.g. for circulating air heating systems, diesel engine air intakes and the like, are commonly sprayed with a gelled oil which helps in removal of solids and liquids from the air being filtered. In such filter units, the collected dust and other impurities are often combustible, and the hazards of fires in flowing air systems are well known. To impart flame resistance to filters used in such systems, the gelled oil sprayed on the filter media is generally phosphate ester, e.g. an alkyl diphenyl phosphate. Gelation is typically accomplished by mixing the ester with a high surface area agent such as SiO.sub.2 powder or with polymers soluble in the ester. Although substantial flame resistance is achieved by such use of phosphate esters, further improvements in flame resistance are very desirable.
Accordingly, it is an object of this invention to provide compositions which may be deposited on solid filter media (e.g. fiberglass) to enhance the efficiency of such media in filtration of solids or liquids from air or other gases and which, when so deposited, will have a high level of flame resistance. Another object is gas filter means comprising solid filter media having deposited thereon such a composition providing the filter means with good flame resistance. Other objects will be apparent from the following in which, except where otherwise noted, percentages are by weight and temperatures are Celsius.